1. Field
The following description relates to a memory device and a method of operating the memory device, and more particularly, to a memory device that manages a buffer in a storage device that uses a buffer memory and a method of managing the memory device.
2. Description of Related Art
Typically, a buffer memory compensates for a difference in speed between two different devices. A device with a relatively moderate speed may be utilized to reduce a delay time, where, for example, there is an interconnection between a device having a higher access speed and a device having a relatively slower access speed. As an example, a cache compensates for a difference in speed between a central processing unit (CPU) and a memory, and a buffer memory compensates for a difference in speed between a host and a storage device, and the like.
Since a cost of the buffer memory is high compared with increase of a processing rate, a memory having a relatively small capacity is used. As an example, a size of a buffer memory of a commonly used hard disk (HDD) is about 4 MB to 32 MB. Accordingly, it is desirable to have a buffer management method that stores data that is needed to be accessed in a short time and that deletes the remaining data, as the amount of data that is storable in a buffer in advance is generally not great.
A buffer management method is also referred to as a buffer replacement algorithm. A first-in first-out (FIFO) algorithm is an exemplary buffer replacement algorithm. FIFO is a method of deleting data from data stored first. Generally, a FIFO algorithm does not consider whether the data will be used in the future, but only considers a sequence of the data that is stored in the buffer. Accordingly, FIFO algorithm is easy implemented.
Another commonly used buffer management method is a least recently used (LRU) algorithm which deletes data where time has elapsed most since a host referred to the data compared to other data. While the LRU algorithm is a practical method, it is more difficult to implement than the FIFO algorithm.
An optimal replacement algorithm may be a method that retains only data that is needed to be accessed in the near future among data stored in a buffer and that deletes the other data. However, such an algorithm is hard to implement, and accordingly, there is need for a buffer replacement algorithm that is closer to an optimal replacement algorithm while being feasible.